<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Document</title>
</head>
<body>

<div id="app">
    <h2 v-if="score>=90">优秀</h2>
    <h2 v-else-if="score>=80">良好</h2>
    <h2 v-else-if="score>=60">及格</h2>
    <h2 v-else>不及格</h2>

    <h1>{{result}}</h1>
</div>

<script src="../js/vue.js"></script>
<script>
    const app = new Vue({
        el: '#app',
        data: {
            score: 99
        },
        computed: {
            result() {
                let showMessage = ''
                if (this.score >= 90) {
                    showMessage = '优秀'
                } else if (this.score >= 80) {
                    showMessage = '良好'
                }
                //...
                return showMessage
            }          
        }
    })
</script>

</body>
</html>